Effects of carbon nanotubes and interphase properties on the interfacial conductivity and electrical conductivity of polymer nanocomposites

L_c is the minimum length of carbon nanotubes (CNTs) required for efficient transfer of filler conductivity to polymer matrix in polymer CNT nanocomposites (PCNTs). In this work, L_c is correlated with the dimensions of the CNTs and the interphase thickness. Subsequently, the interfacial conductivity as well as the effective length and concentration of CNTs are expressed by CNT and interphase properties. Moreover, a simple model for the tunneling conductivity of PCNTs is developed with these effective terms. The impacts of all parameters on L_c, the interfacial conductivity, the fraction of CNTs in the networks and the conductivity of the PCNT are explained and justified. In addition, the predictions of the percolation threshold and conductivity are compared with the experimental results of several samples. The desirable values of interfacial conductivity are achieved by thin, short and super‐conductive CNTs, high waviness and a thick interphase. However, thin and long CNTs, low waviness, a thick interphase, poor tunneling resistivity due to the polymer matrix and a short tunneling distance advantageously affect the conductivity of PCNTs, because they produce large conductive networks. The predictions also show good agreement with the experimental measurements of percolation threshold and conductivity, which confirms the developed equations. © 2020 Society of Chemical Industry     

复合顶板动压巷道围岩应力演化和支护技术研究

三交河矿10_^#下煤层顶板为典型复合岩层,从已掘巷道来看,10_^#下煤层巷道顶板成型不佳,容易风化破碎,受采动影响下易出现顶板离层破碎下沉等破坏现象。10-2032巷为复合顶板条件采掘对穿巷道,支护难度较大,在分析地质条件的基础上,通过数值模拟,对10-2032巷与10-201回采面对穿前后的应力状态进行了分析。结合应力演化情况和锚杆支护原理,根据工程类比和数值模拟结果,提出10-2032巷锚杆锚索支护设计。顶板采用长短锚索组合支护,两帮采用单体锚杆搭配W钢护板支护,井下实践证明,与相邻回采面对穿后,2032巷仍能保持较好的支护效果。     

Investigation on the mechanism of charge generation in organic heterojunctions: Analysis of I–V and C–V characteristics

The charge generation mechanism of organic heterojunction (OHJ) consisted of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) and different hole transporting materials (HTMs) are studied systematically by current-voltage (I–V) and capacitance-voltage measurements. The analysis of I–V characteristics of the devices based on OHJs at forward and reverse voltages by comparing the thickness of HTM layers finds that a forward and reverse symmetrical I–V curve is observed at thin HTM layers and the forward current becomes larger than the reverse current with the increase of HTM thickness, fully illustrating the effectiveness of OHJ charge generation. Moreover, the I–V characteristics at different temperatures indicate that the efficient charge generation is originated from electron tunneling rather than diffusion. And the C–V and capacitance-frequency (C–F)characteristics further illustrate the highly efficient charge generation ability of OHJs so that the charge density is as high as 4.5 × 10¹⁷ cm⁻³, guaranteeing the high conductivity of OHJs, which is very beneficial to developing highly efficient OLEDs using OHJs as charge injector and generator.     

长距离定向钻进技术在巷道掘进超前探查中的应用研究

巷道掘进超前探查一般采用钻探方法的开展工作,常规回转钻进由于受钻进工艺等影响,存在钻孔施工长度短、影响正常掘进、施工精度较差等问题。而采用长距离掩护式定向钻进工艺开展超前探放水工作,可对掘进头600m范围内进行超前探查,钻孔施工长度较常规回转钻进孔长度增大3~4倍,在不影响掘进的前提下,可通过随钻测斜仪器实时对钻孔轨迹进行调整、监控,从而达到高精度、长距离对掘进前方进行超前探查,较常规超前探放水具有较大的优势[1]。     

An energy‐dissipating approach for adjacent retrofitted structures

The approach of positioning energy dissipaters between adjacent structures can effectively prevent the collision of two adjacent buildings. For adjacent retrofitted structures, an effective strengthening approach that involves implementing energy‐dissipation measures both between and within buildings is proposed. This paper is based on the actual Shanghai ShiMao International Plaza. To avoid having to strengthen most of the structural members, the strengthening measure of energy dissipation is selected because of its construction cost and time constraints. This approach involves replacing several dampers between the adjacent structures and adding viscous damping walls in the retrofitted structure to reduce the seismic response of the retrofitted structure back to the original level. Additionally, a practical calculating method for the equivalent additional damping ratio for the adjacent structures connected by energy dissipaters is proposed. The results show that the effect of energy dissipation in the retrofitted structure is prominent and that the goal of indirect strengthening is achieved. The strengthening approach of energy dissipation and the calculating method of the equivalent additional damping ratio for adjacent structures provide a reference for similar engineering designs.     

Opportunities and Challenges in Tunneling Nanotubes Research: How Far from Clinical Application?

Tunneling nanotubes (TNTs) are recognized long membrane nanotubes connecting distance cells. In the last decade, growing evidence has shown that these subcellular structures mediate the specific transfer of cellular materials, pathogens, and electrical signals between cells. As intercellular bridges, they play a unique role in embryonic development, collective cell migration, injured cell recovery, cancer treatment resistance, and pathogen propagation. Although TNTs have been considered as potential drug targets for treatment, there is still a long way to go to translate the research findings into clinical practice. Herein, we emphasize the heterogeneous nature of TNTs by systemically summarizing the current knowledge on their morphology, structure, and biogenesis in different types of cells. Furthermore, we address the communication efficiency and biological outcomes of TNT-dependent transport related to diseases. Finally, we discuss the opportunities and challenges of TNTs as an exciting therapeutic approach by focusing on the development of efficient and safe drugs targeting TNTs.     

Silicene Nanoribbons on an Insulating Thin Film

Silicene, a new 2D material has attracted intense research because of the ubiquitous use of silicon in modern technology. However, producing free-standing silicene has proved to be a huge challenge. Until now, silicene could be synthesized only on metal surfaces where it naturally forms strong interactions with the metal substrate that modify its electronic properties. Here, the authors report the first experimental evidence of silicene nanoribbons on an insulating NaCl thin film. This work represents a major breakthrough, for the study of the intrinsic properties of silicene, and by extension to other 2D materials that have so far only been grown on metal surfaces.     

扫描隧道显微镜钨针尖的制备与表征

采用直流电化学刻蚀方法制备扫描隧道显微镜钨针尖,研究了电化学刻蚀过程中NaOH溶液浓度、钨丝浸入长度和刻蚀电压对针尖形貌的影响。通过扫描电子显微镜(SEM)测量针尖曲率半径和针尖纵横比值,以表征针尖的尺寸和形状;通过能谱仪(EDS)分析针尖表面成分,以表征表面清洁度;通过场发射显微镜(FEM)得到Fowler-Nordheim (F-N)曲线来检测针尖发射性能。实验结果表明,当溶液浓度为2 mol/L、钨丝浸入长度为4 mm、刻蚀电压为3 V时,可以得到曲率半径约为100 nm、纵横比值为13的针尖,且表面无钨的氧化层。FEM结果显示当对针尖施加500 V的负偏压时,针尖可以稳定发射50 nA量级的电流,且针尖性能具有良好的一致性。     

相邻雷达回波强度差异分析

文章选用2017-12-13的青浦站和南通站体扫数据和单站格点CAPPI数据,利用时空一致性匹配法和单站格点数据等距离线法对两站雷达回波强度差异情况进行了研究,并分析了两种算法可能存在的误差,结果表明:单站格点数据等距离线法要优于时空一致性匹配法,更适用于单部雷达体扫数据的相邻雷达回波差异对比;在雷达基数据正确的情况下,时空一致性匹配法误差主要来源于做不到真正的时空匹配一致,格点数据等距离线法误差主要来源于生成格点数据时插值算法不完善。     

义能煤矿岩巷快速施工设备及配套工艺研究

义能煤矿一直采用风锤打眼爆破、耙装机装岩、矿车排矸的方式进行岩石巷道掘进。岩石巷道掘进机械化水平较低、工人劳动强度比较大、掘进速度缓慢。为了突破岩石巷道快速掘进的瓶颈,配备岩巷凿岩、装岩、排矸机械化作业是岩巷快速掘进的先决条件,优化爆破参数及爆破方案是关键,完善支护参数是基础,科学合理的施工组织是实现快速掘进的前提。